The present invention relates to the field of construction products, and, more particularly, to a lightweight, high-strength, fire-resistant, and moisture-resistant backerboard sheet as may be used in areas subject to moisture and splashing and as may used as a backing substrate for tile.
Wallboard sheets are widely used in building construction to form partitions or walls of rooms, elevator shafts, stair wells, ceilings, etc. The sheets are typically fastened to a suitable supporting framework. The seams between sheets are covered to provide an even wall surface. The sheets may be readily cut to size by first scoring the face sheet, and then snapping the board about the score line. The wall may then be painted or covered with a decorative wall covering, if desired. Such wallboard sheets created from a gypsum core with outer face layers of paper, sometimes referred to as gypsum board or drywall, are well known.
Gypsum wallboard is typically manufactured by delivering a slurry or paste containing crushed gypsum rock onto a moving sheet of facing paper to which a second or top paper layer is then added to form a long board line. The board line permits the slurry to harden before being cut. The cut panels are heated in a kiln, before being packaged for storage and shipping.
Typically, such sheets are xc2xd or ⅝ inch thick and in conventional sizes of 4xc3x978 feet, such a gypsum wallboard sheet may weigh about 55-70 pounds. Accordingly, handling of such gypsum wallboards presents a significant task for construction personnel or wallboard xe2x80x9changersxe2x80x9d, particularly when such boards are secured overhead to form a ceiling. In addition, the fire resistance, thermal insulation and sound absorbing properties of conventional gypsum wallboard sheets may not be sufficient for some applications.
Another variation of gypsum wallboard is water-resistant drywall or xe2x80x9cgreenboardxe2x80x9d. The greenboard typically includes the same gypsum core, but includes a water-resistant facing so the water is less likely to penetrate, stain and/or decay the wall. Greenboard is typically used for walls in a moist or humid environment, such as a bathroom, for example. Such greenboard is not typically recommended as an underlayment for tile in the bathroom, for example, since water may penetrate the grout or cracks between adjacent tiles and deteriorate the greenboard. U.S. Pat. No. 5,552,187 to Green et al. discloses the addition of a fibrous mat-faced gypsum board coated with a water-resistant resinous coating for greater durability in moist environments.
Yet another related conventional wallboard product to serve as an underlayment for wet areas is the concrete backerboard. For example, UTIL-A-CRETE(copyright) Backerboard from Bonsal is a precast cementitious backboard with glass mesh reinformcement. The board includes portland cement, fiber glass mesh and lightweight aggregate. The backerboard is more adapted to be used in areas subject to splashing or high moisture.
While the glass mesh face layers are typically secured to the surface of the backerboard after the core has been precast, continuous production is also disclosed in U.S. Pat. No. 5,221,386 to Ensminger et al. In addition, the mesh or reinforcing layers have also been embedded in the faces and edges of the backerboards.
Unfortunately, conventional cementitious backerboards may be more difficult to score and break to size. Moreover, since the backerboards include a core of cement, their density is considerably greater than even conventional gypsym wallboard. Accordingly, manufacturers may offer the backerboards in smaller sizes to be more readily handled by the installer, but such increases seams between sheets and also increases costs of installation. A typically-sized 4 foot by 8 foot sheet can weigh well over 100 pounds, which is very unwieldy especially in confined spaces.
In view of the foregoing background, it is therefore an object of the invention to provide a backerboard sheet for moist areas which is relatively lightweight, strong, has good fire resistance, thermal insulation, and sound absorbing properties.
This and other objects, features and advantages in accordance with the invention are provided by a backerboard sheet comprising a core having opposing first and second major surfaces, at least one moisture-resistant face layer on at least one of the first and second major surfaces of the core; and wherein the core comprises aerated concrete. The provision of aerated concrete for the core provides many key advantages over conventional backerboard sheets, such as gypsum greenboard or cementitious backerboard, for example.
The at least one moisture-resistant face layer may comprise fibers, such as arranged in a woven mesh. The fibers may include at least one of glass, plastic, and metal. In addition, the at least one moisture-resistant face layer may further comprise a moisture-resistant material incorporating the fibers, such as a suitable resin, for example.
The at least one moisture-resistant face layer may comprise first and second moisture-resistant face layers on respective first and second major surfaces of the core. The core may also have a generally rectangular shape defining a pair of opposing side edges and a pair of opposing end edges. The first major surface in some embodiments may have beveled portions adjacent respective opposing side edges.
The at least one moisture-resistant face layer may extend around the opposing side edges, and leaving the opposing end edges of the core exposed.
The aerated concrete core may have a relatively low density in a range of about 25 to 40 lbs./ft.3 The core may also have a thickness in a range of about xc2xc to 1 inch, a width in a range of about three to five feet, and a length in a range of about five to sixteen feet. Accordingly, even a 1 inch thick, 4 foot by 8 foot backerboard sheet may have a relatively low total weight of about 60 pounds.
The core may further comprise reinforcing fibers in the aerated concrete. For example, the reinforcing fibers comprise cellulose, and/or glass.
The backerboard sheet is readily manufactured, and may include a joint therein as a result of the manufacturing process. The joint can be stronger than the adjacent core material, and without compromising the ability to score and snap break the sheet as conveniently as with conventional backerboard sheets. In other words, some embodiments of the sheet may include first and second portions aligned in end-to-end relation at respective opposing edges thereof, and an adhesive layer joining the opposing edges of the first and second portions together.